A variety of drag reducers have been used in the past to reduce pressure loss associated with turbulent flow of a fluid through a pipeline. Ultra-high molecular weight polymers are known to function well as drag reducers. In general, increasing the molecular weight and concentration of the polymer in the drag reducer increases the effectiveness of the drag reducer, with the limitation that the polymer must be capable of dissolving into the host fluid. However, drag reducers containing large concentrations of high molecular weight polymers generally can not be transported through small lines over large distances because certain types of drag reducers with high viscosities (e.g., gel-type drag reducers) require unacceptably high delivery line pressures and other types of drag reducers containing polymer particles (e.g., suspension-type drag reducers) can plug the delivery lines. In the past, gel and suspension drag reducers have not been delivered to subsea locations because economical subsea delivery would require passage through long conduits having small diameters.
It has recently been discovered that certain types of latex drag reducers can be effectively transported through long conduits having small diameters because such drag reducers have a relatively low viscosity and contain relatively small particles of the drag-reducing polymer. However, the presence of water in latex drag reducers presents a potential drawback for implementing such drag reducers in applications where they might come into contact with natural gas under conditions of low temperature and/or high pressure (e.g., subsea conditions). When a water-containing latex drag reducer contacts natural gas at low temperatures and/or high pressures, natural gas hydrates may form. If gas hydrates form in the conduit carrying the drag reducer, the conduit can become plugged. Thus, water-containing latex drag reducers have not been employed for subsea applications where they might come into contact with natural gas at low temperatures and high pressures.